The present invention relates to methods for controlling fluid loss in a subterranean formation.
Hydrocarbons (oil, condensate, and gas) are typically produced from wells that are drilled into the formations containing them. For a variety of reasons, such as inherently low permeability of the reservoirs or damage to the formation, such as caused by drilling and completion of the well, the flow of hydrocarbons into the well may be undesirably low. In such cases, the well may be “stimulated,” for example by the introduction of fracturing or acidizing fluids.
In order to treat a formation efficiently, a fluid loss additive may first be introduced into the formation to prevent fluid leak off and to plug thief zones where treatment fluid may leak into the rock matrix or fractures of the formation. This is usually accomplished by pumping non-degradable materials such as silica flour, fine mesh proppant, mica and cellulose materials. Because these materials do not degrade, however, they may be difficult to remove or clean up after the desired treatment has been carried out. Remaining materials may cause permanent damage and reduce hydrocarbon production from the formation. Dissolvable materials such as rock salt or benzoic acid flakes have been used as a temporary diverting or fluid loss agent. The degradation rates of such materials are difficult to control, however.
Better methods for fluid diversion and controlling leak off of treatment fluids are therefore needed.